U.S. patent application number 10/250781 was filed with the patent office on 2004-04-01 for oil well perforator.
Invention is credited to Bourne, Brian.
Application Number | 20040060734 10/250781 |
Document ID | / |
Family ID | 9908196 |
Filed Date | 2004-04-01 |
United States Patent
Application |
20040060734 |
Kind Code |
A1 |
Bourne, Brian |
April 1, 2004 |
Oil well perforator
Abstract
This invention relates to the field of oil wells and in
particular to the explosive and other devices that are used to
perforate oil well casings and hydrocarbon bearing rocks in order
to create channels through which oil and gas can flow into the well
bore. Existing oil well perforators are either termed "big hole"
perforators which are designed to produce large holes in the oil
well casing only or "deep hole" perforators which are designed to
perforate the casing of the well into the surrounding rocks. This
invention proposes a novel "dual action" perforator capable of
substantially performing the same functions as both deep hole and
big hole perforators.
Inventors: |
Bourne, Brian; (Sevenoaks,
GB) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
1100 N GLEBE ROAD
8TH FLOOR
ARLINGTON
VA
22201-4714
US
|
Family ID: |
9908196 |
Appl. No.: |
10/250781 |
Filed: |
July 9, 2003 |
PCT Filed: |
January 23, 2002 |
PCT NO: |
PCT/GB02/00275 |
Current U.S.
Class: |
175/4.6 ;
166/297; 166/55.1 |
Current CPC
Class: |
F42B 1/02 20130101; E21B
43/117 20130101 |
Class at
Publication: |
175/004.6 ;
166/297; 166/055.1 |
International
Class: |
E21B 043/118 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 6, 2001 |
GB |
0102914.9 |
Claims
1. A tandem oil well perforator comprising i) a substrate, ii) a
linear cutting charge mounted upon the substrate iii) first
detonation means for detonating the cutting charge iv) at least one
hollow liner shaped charge mounted upon the substrate, and; v)
second detonation means for detonating the hollow liner shaped
charge wherein vi) the substrate, cutting charge and the at least
one shaped charge are adapted for location within an oil well, and
vii) the substrate, cutting charge and the at least one shaped
charge are configured such that in use detonation of the cutting
charge by the first detonation means cuts a hole in the oil well
casing and detonation of the at least one shaped charge by the
second detonation means causes a highly penetrating jet or jets to
be projected through the hole in the casing.
2. A tandem oil well perforator as claimed in claim 1 wherein the
substrate is friable.
3. A tandem oil well perforator as claimed in claim 2 wherein the
friable substrate comprises a blown ceramic material.
4. A tandem oil well perforator as claimed in any preceding claim
and further comprising means for causing a small time delay between
the detonation of the first detonation means and the detonation of
the second detonation means.
5. A tandem oil well perforator as claimed in any preceding claim
wherein the first detonation means also acts as the second
detonation means.
6. A tandem oil well perforator as claimed in any preceding claim
wherein the cutting charge is arranged in use to be at a
substantially constant distance from the casing of the oil
well.
7. A tandem oil well perforator as claimed in claim 4 wherein the
cutting charge is arranged in use to be at a distance of
approximately one gape length from the casing.
8. A tandem oil well perforator as claimed in any preceding claim
wherein the shaped hollow charge liner material comprises a
tungsten rich alloy.
9. A method of producing holes in the casing of oil wells and
simultaneously producing perforation into the area surrounding the
oil well comprising the steps of: i) placing an oil well perforator
according to any of claims 1 to 8 in an oil well at a location
where it is desired to produce a hole; and ii) detonating the oil
well perforator.
10. A tandem oil well perforator comprising i) a substrate, ii) a
first hollow liner shaped charge mounted upon the substrate iii)
first detonation means for detonating the first hollow liner shaped
charge iv) a second hollow liner shaped charge mounted upon the
substrate; and v) second detonation means for detonating the second
hollow liner shaped charge wherein vi) the substrate and shaped
charges are adapted for location within an oil well, and vii) the
substrate and shaped charges are configured such that in use
detonation of the first hollow liner shaped charge by the first
detonation means cuts a hole in the oil well casing and detonation
of the second hollow liner shaped charge by the second detonation
means causes a highly penetrating jet to be projected through the
hole in the casing, the detonation of the shaped charges being
sufficient to disintegrate the friable substrate.
11. A tandem oil well perforator as claimed in claim 10 wherein the
substrate is friable.
12. A method of producing holes in the casing of oil wells and
simultaneously producing perforation into the area surrounding the
oil well comprising the steps of: i) placing an oil well perforator
according to claims 10 or 11 in an oil well at a location where it
is desired to produce a hole; and ii) detonating the oil well
perforator.
Description
[0001] This invention relates to the field of oil wells and in
particular to the explosive and other devices that are used to
perforate oil well casings and hydrocarbon bearing rocks in order
to create channels through which oil and gas can flow into the well
bore.
[0002] The metal casing of an oil well bore is surrounded by cement
which is in turn in contact with the hydrocarbon bearing rocks. Oil
well perforators generally perforate oil well casings in one of two
ways. Deep hole perforators are designed to produce a high level of
perforation through the metal casing and cement into the
hydrocarbon bearing rocks. Big hole perforators are designed to
produce large holes in the casing only.
[0003] Existing perforators are deployed down the oil well casing
by mounting them in a gun and hundreds may be used at any one
time.
[0004] Both deep hole and big hole perforators use a form of shaped
hollow charge. In its most common configuration a shaped charge
consists of a cylindrical tubular casing containing a hollow metal
liner, mounted so that its axis of symmetry is coincident with that
of the casing. The liner shape is most commonly conical although
other geometries such as hemispheres or trumpets can be used. The
base of the liner is at the end of the cylinder facing the target
and explosive is packed within the casing and around the outside of
the liner. When the explosive is detonated at the end of the
cylinder furthest from the target, a detonation front sweeps the
liner causing it to collapse and produce a high velocity jet of
liner material which is directed towards the target. A history of
shaped charge warheads can be found in Fundamentals of Shaped
Charges by Walters W P and Zukas J A (ISBN 0-471-62172-2
(1989)).
[0005] The hollow liners used in big hole perforators are generally
parabolic in shape and are made of 60Cu/40Zn brass. The apex of the
liner has a hole in it which facilitates the formation of a large
diameter jet (larger than if the liner surface continued all the
way to the apex). For typical pipe diameters (on the order of 100
mm), big hole perforators have a diameter of approximately 42 mm
with a hole of diameter 10 mm in the apex of the liner. This
configuration is capable of producing a hole of approximately 20-25
mm in the oil well casing.
[0006] A drawback of shaped charge based perforators is that the
geometry of the shaped charge is incapable of producing a hole
greater than that of the diameter of the charge. Shaped charge
based big hole perforators are therefore limited in the size of
hole they can produce (Larger holes can be produced mechanically by
milling or grinding for example, but these processes are time
consuming and costly).
[0007] The shaped charges used in deep hole perforators, in
contrast to the big hole perforators, do not have holes in the apex
of the liner material. For these perforators a narrow, fast moving
jet is required to provide a high level of perforation through the
casing, concrete and hydrocarbon bearing rock. The deep hole
perforators should also be low cost and amenable to high volume
production.
[0008] It is clear that the differing geometries of the deep hole
and big hole perforator shaped charges mean that it is not usually
feasible to use a single charge to achieve both effects
simultaneously. However, the highest oil and gas flows would be
achieved by producing a large hole in the casing and at the same
time a high level of perforation through the casing, concrete and
hydrocarbon bearing rock.
[0009] It is therefore an object of the present invention to
provide a "dual action" oil well perforator which is substantially
capable of performing the same functions as both deep hole and big
hole perforators.
[0010] Accordingly this invention provides a tandem oil well
perforator comprising
[0011] i) a substrate,
[0012] ii) a linear cutting charge mounted upon the substrate
[0013] iii) first detonation means for detonating the cutting
charge
[0014] iv) at least one hollow liner shaped charge mounted upon the
substrate; and
[0015] v) second detonation means for detonation the hollow liner
shaped charge
[0016] wherein
[0017] vi) the substrate, cutting charge and the at least one
shaped charge are adapted for location within an oil well, and
[0018] vii) the substrate, cutting charge and the at least one
shaped charge are configured such that in use detonation of the
cutting charge by the first detonation means cuts a hole in the oil
well casing and detonation of the at least one shaped charge by the
second detonation means causes a highly penetrating jet or jets to
be projected through the hole in the casing.
[0019] The substrate should be any suitable means of supporting the
charges in a manner that will not interfere with their operation.
For example, the charges could be carried on a friable substrate
which disintegrates upon detonation of the charges. Alternatively,
a conventional gun deployment system which is common in the oil and
gas industries may be used. Such gun systems would be sufficiently
robust to be withdrawn from the well bore after firing. A further
alternative would be a so-called "full flow gun system". Such a gun
system would be arranged to disintegrate upon firing in much the
same way as the friable substrate mentioned above.
[0020] In the case of a friable substrate, the substrate should be
sufficiently friable such that following detonation of the cutting
charge and shaped charge(s) it disintegrates and the debris falls
down the oil well pipe. Preferably therefore the substrate is made
of a blown ceramic material. Such materials are relatively light
and are capable of easy machining thereby allowing complex shaped
grooves to be created for support of the cutting charge/shaped
charge(s). Such materials are also sufficiently robust to be
deployed down the pipe. An example of a suitable ceramic material
is AL 203 manufactured by Friatec DPL in France.
[0021] This invention utilises explosive cutting charges to cut the
oil well casing. Such charges can be flexible linear shaped charges
comprising explosive which has been extruded together with a metal
or plastic sheath (The cutting charge may be copper, silver or
polymer lined). However, other versions of explosive cutting
charges may be rigid and pre-formed into a preferred shape or
configuration. These cutting cords can be made into any size and
can be configured into any shape required. In use these charges
chop the well bore casing into pieces that do not subsequently
interfere with down hole activities.
[0022] A hollow liner shaped charge is then used to provide a high
level of perforation through the hole in the casing and into the
surrounding concrete and hydrocarbon bearing rocks. The substrate
may carry one or more of these shaped charges depending on the
level of deep hole penetration required. If multiple shaped charges
are used they can conveniently be formed into a focussing array for
greater penetrative power.
[0023] The use of two perforating charges in a down hole
environment enhances oil and gas flow and also enhances other
activities such as the deployment of instrumentation and
sensors.
[0024] Conveniently there is a time delay between the detonation of
the cutting charge and the detonation of the shaped charge(s).
Traditionally, a shaped charge is detonated by detonating the
explosive at that part of the shaped charge which is furthest from
the target. Therefore, a small time delay can be inserted between
the firing of the first and second detonation means.
[0025] However, a shaped charge can be reverse initiated, i.e. the
charge can be detonated by detonating the explosive that lies at
the points closest to the target (For the case of a conical liner
this would equate to initiating detonation at the periphery of the
base of the cone). Therefore, conveniently if the shaped charge is
reverse initiated then the fit detonation means can also be used as
the second detonation means.
[0026] The gape of the cutting cord (which is defined as the
distance across the mouth of the linear charge) can be made into
any size appropriate to the thickness of the metal to be cut. The
cutting cords should be at a reasonably constant distance from the
metal to be cut, preferably around one gape length.
[0027] Preferably the shaped charge(s) should be lined with a
material known to be effective at penetrating concrete. Copper or
preferably a very dense material such as a tungsten rich alloy
should be used. However, other wrought or green compacted powder
liner material, both metallic and non-metallic, may be equally
advantageous.
[0028] Conveniently the invention can be mounted on a reusable gun
arrangement similar to existing systems.
[0029] Correspondingly there is provided a method of producing
holes in the casing of oil wells and simultaneously producing
perforation into the area surrounding the oil well comprising the
steps of:
[0030] i) placing an oil well perforator according to the present
invention in an oil well at a location where it is desired to
produce a hole; and
[0031] ii) detonating the oil well perforator.
[0032] In a second aspect of the invention, a dual action oil well
perforator comprises a conventional deep hole perforator and a
conventional big hole perforator operating in tandem. According to
this second aspect of the invention a tandem oil well perforator
comprises
[0033] i) a substrate,
[0034] ii) a first hollow liner shaped charge mounted upon the
substrate
[0035] iii) first detonation means for detonating the first hollow
liner shaped charge
[0036] iv) a second hollow liner shaped charge mounted upon the
substrate; and
[0037] v) second detonation means for detonating the second hollow
liner shaped charge
[0038] wherein
[0039] vi) the substrate and shaped charges are adapted for
location within an oil well, and
[0040] vii) the substrate and shaped charges are configured such
that in use detonation of the first hollow liner shaped charge by
the first detonation means cuts a hole in the oil well casing and
detonation of the second hollow liner shaped charge by the second
detonation means causes a highly penetrating jet to be projected
through the hole in the casing, the detonation of the shaped
charges being sufficient to disintegrate the friable substrate.
[0041] Similar substrate configurations as described for the first
aspect of the invention above can be used in this second aspect of
the invention.
[0042] Correspondingly there is provided a method of producing
holes in the casing of oil wells and simultaneously producing
perforation into the area surrounding the oil well comprising the
steps of:
[0043] iii) placing an oil well perforator according to the second
aspect of the present invention in an oil well at a location where
it is desired to produce a hole; and
[0044] iv) detonating the oil well perforator.
[0045] In this second aspect of the invention a conventional big
hole perforator first cuts a hole in the oil well casing and then a
conventional deep hole perforator provides a high level of
perforation through the hole in the casing and into the surrounding
concrete and hydrocarbon bearing rocks. The dimensions of typical
perforator charges means that this second aspect of the invention
is more conveniently deployed in larger diameter pipes of the order
12 centimetres in diameter and above.
[0046] Embodiments of the oil well perforator according to the
present invention will now be described with reference to the
accompanying drawings in which:
[0047] FIG. 1 shows a view of the tandem perforator and oil well in
cross section
[0048] FIG. 2 shows the oil well casing and oil well perforator in
cutaway
[0049] FIG. 3 shows the oil well in cross section after the
perforator has been fired
[0050] FIG. 4 shows alternative ways of initiating detonation of
the perforator
[0051] FIG. 1 shows an oil well that has been bored into
hydrocarbon bearing rocks 1. The oil well comprises a metal casing
3 which is surrounded by a concrete layer 5 which separates it from
the rocks 1.
[0052] The oil well perforator (7, 9, 11) comprises a friable
substrate 7, a cutting charge 9 and a shaped charge 11. (The
detonators for the cutting charge and shaped charge are not
shown).
[0053] FIG. 2 shows a 3-dimensional view of part of the metal pipe
3 depicted in FIG. 1 (Note: like numerals are used to denote like
features). A window 13 has been cut away in the side of the pipe in
order to show the configuration of the cutting charge 9 upon the
substrate 7. The configuration of the cutting charge 9 will be
dependent upon the hole desired in the metal casing 3. In this case
the cutting charge has been formed into an approximation of a
spoked wheel. The shaped hollow charge 11 is visible at the centre
of the wheel arrangement.
[0054] Upon detonation of the cutting charge 9 by the first
detonator (not shown) a hole will be cut in the metal casing 3. For
the configuration shown a hole similar to the cutaway window 13
will be formed. After a short time delay the second detonator will
detonate the shaped hollow charge 11 which will penetrate the
concrete and rock beyond the hole in the casing. Debris from the
casing 3 and the substrate 7 will fall down the well.
[0055] The detonation of the cutting charge 9 will be a complex
procedure but it should be designed such that the cord element on
the periphery of the wheel detonates substantially
simultaneously.
[0056] FIG. 3 depicts the cross sectional view of FIG. 1 after the
tandem perforator has been fired. The perforator (7, 9, 11) and
casing fragments have now fallen down the well and are no longer
visible. The detonation of the shaped hollow charge has produced a
deep hole 15 in the concrete and rock.
[0057] FIG. 4 depicts various ways of initiating the perforator (7,
9, 11) shown in FIGS. 1 and 2. The perforator comprises a shaped
hollow charge 11 and cutting cord 9. In a traditional mode of
operation the cutting cord will first by detonated by first
detonation means (not shown) at positions 20. After a short time
delay the shaped hollow charge will be initiated by the second
detonator (not shown) at position 22 resulting in a penetrating jet
in the direction 24.
[0058] In an alternative mode of operation the first detonator also
acts as the second detonator. In this case the tandem perforator is
initiated at positions 26. This results in the detonation of the
cutting cord almost simultaneously and the reverse initiation of
the shaped hollow charge. This removes the requirement to build in
a time delay between two separate detonators.
[0059] Other ways of configuring the cutting charge and shaped
charge will be readily apparent to the skilled person.
* * * * *